Improvement in piston-valves for steam-engines



v UNITED STATES PATENT OFFICE..y

ROBERT H. LEOKY, OF ALLEGHENY, PENNSYLVANIA.

IMPROVEMENT IN PISTON-VALVES FOR STEAM-ENGINES.

Specification forming part of Letters Patent No. 39,4S5, dated August 11, 1863.

To all whom it may concern:

Be it known that I, ROBERT H. LEGKY, of Allegheny city, in the county of Allegheny and State of Pennsylvania, have invented a new and improved mode of constructing and operating piston-valves for Steam-En gines, so as to relieve the valve entirely from the usual load of pressure and the friction of the valve-rod packing 5 and I do hereby declare that the following is a full and exact description thereof, reference being had to the accompanying drawings, and to the letters of reference marked thereon.

The nature of my invention consists in providing the side pipe or steam-chest of steamengines with a piston-valve, arranged so that there can be no pressure or load on the valve or its seat, which I accomplish by introducing the steam into said side pipe or steam-chest, between steam-tight heads on the valve, so that the pressure will be equal in all directions, the whole being arranged and constructed as hereinafter described.

To enable others skilled in the art to make and use myimprovement, Iwill proceed to describe its construction and operation.

In the accompanying drawings, Figure l is a side or top view of a cylinder and side pipe or steam-chest of a steam-engine. Fig.2 is a view of the same in section through its center.

A is the cylinder; O is the side pipe or steamchest, open at both ends, and bored out like the cylinder; D, the piston-head. t' t' are the usual ports or passages leading from the side pipe to the cylinder. E is the valve-rod,on which are the heads F F and g g, which heads are provided with followers and packing to keep them steam-tight. h It are exhaust-ports leading from the side pipe to the escape-pipe or heater. B is the steam-pipe connecting the throttle-valve with steam-chamber L, formed by the heads g and F in the sidepipe. K and K are also two chambers for the purpose of permittin g the exhaust to pass freely through the side pipe while the valve is in motion. The valve rod E is atttached to the wrist on the rocker or link by a strap-joint, and the side pipe, O, being open at both ends, the valve and rod can be removed at any time by disconnecting the strap-joint aforesaid. The valve-rodE is fitted with a screw-thread, so that the position of the heads F F and g g can be varied at pleasure and to any point, to give more or less lap, as desired. The exhaust-spaces K K will be needed just long enough in length so that the heads F F and g g will never close the openings h and h when the Valve is at any point in its travel, and that one of the openingsz' and one of the exhaust-openings h shall be contained between either F F or g g, while the other end is receiving steam through the port t' from the chamber L. (See Fig. 2.) The valve-rod can be made hollow, and the inner heads screwed up from without, or the side pipe, C, can be fitted withan opening in the chamber L, to be closed with an arch and plate, and to be removed when it is necessary to tighten ,the packings of the valve.

The operation of my improvement is as follows: The steam enters the side pipe, G, Ihrou gh the pipe B and, filling the chamber L between the heads g and F, on each of which it presses equally, thus throwing the strain or load of pressure from the seat of the valve to that part of the rod between the heads g and F, producing an equilibrium, and thus relieving the engine of the entire valve-pressure. In the drawings the course of the steam is indicated by the arrows, the forward end receiving and the after end exhausting, and of course the like result is produced (by sliding the valve) on the other end, as shown by the dotted lines. The steam will be shut oft' from both ends and both exhausts opened by placing the valve on its center.

lt will be observed that by my improved valve the only power needed to drive it is required by the simple friction of the packed heads g g and F F, and that the valve will move as lightly with the steam on as when emp y. The ends of the side pipe, C, being open of course no packing is needed on the valve-rod. Any amountof lead or lap can be given to both steam and exhaust by simply varying the position of the heads g g and F F on the rod E. This arrangement may be just reversed and the steam admitted through openings h and h, and the exhaust thrown into the center chamber, L, and out of pipe B, if desired; but I prefer the other, as it reduces the number of heads exposed to the live steam, and of course saves the packing and enables me to make the outer exhaust-heads much lighter in construction, &c., the exhaust requiring but little confinement in its passage to the escapepipe. In the drawings the steam-openingsi and/t' are nearer to the cylinder than would be the ease if the steam was admitted through the outer chambers K K instead of through chamber L. The same arrangement can be partly carried out, and the like result produced, with a iiat sliding valve formed with the chambers K L and K in it, and sliding between the seat and a plate or cap of a steamchest, and having the ports h h and the opening of pipe B made either at the seat or cap above, but the lap or lead 'could not be so nicely Varied, nor the whole thing gotten up so simple and efficient. 

